Sex and weight differences between a deceased kidney donor and a recipient may boost the risk of graft loss, a new study finds.

Of 115,124 deceased donor kidney recipients from the Scientific Registry of Transplant Recipients 2000 to 2014, 21,261 experienced graft failure after a median 3.8 years, according to results published online in the Clinical Journal of the American Society of Nephrology.

The highest risk for graft failure (50%) was found for female recipients of male donor kidneys and male recipients of female donor kidneys when the recipient was more than 30 kg (66 pounds) heavier than the donor. Male recipients who were heavier than their female kidney donors had the next highest risk of graft failure at 35%. Results for the combined mismatch held when the researchers used body surface area instead of weight. Investigators adjusted results for other known predictors of kidney transplant failure, including cold ischemia time and donor cause of death; human leukocyte antigen mismatch; panel reactive antibody; end-stage renal disease cause, and dialysis vintage; and in donors and recipients, comorbidities, age, race, and height.  

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The magnitude of the increased risk of graft loss from a weight and sex mismatch combined was on par with the donor having diabetes or the recipient receiving dialysis for more than 4 years.

“This study is extremely important because we have shown that when all else is considered, something as simple as the combination of a kidney donor’s weight and sex is associated with a marked increase in kidney transplant failure,” lead investigator Amanda Miller, MD, of Nova Scotia Health Authority in Halifax, Nova Scotia, Canada, stated in a news release. “While more research is required before including these variables in a recipient matching strategy, this study highlights the importance of donor and recipient matching above and beyond current immunology-based protocols.”

Sensitization and relative nephron mass might explain the findings, Dr Miller and colleagues suggested. “The potential synergistic increase in graft loss we demonstrated in the setting of combined weight and sex mismatch (particularly in MDFR) may be due to an added immunologic strain imposed on a reduced number of nephrons with exaggerated compensatory hyperfiltration and subsequent injury.”

In an accompany editorial, Bethany Foster, MD, MSCE, and Indra Gupta, MD, of McGill University in Quebec, Canada, urged “a great deal of caution” before incorporating such criteria into organ allocation.

“Whether such complex matching would lead to meaningful improvements in graft survival is not known,” they wrote. “More importantly, special care would have to be taken to avoid disadvantaging larger recipients.” In particular, women, who have greater risks of sensitization, and those with a larger body size might be forced to wait longer for a kidney transplant.

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1. Miller AJ, Kiberd BA, Alwayn IP, Odutayo, and Tennankore KK. Donor-Recipient Weight and Sex Mismatch and the Risk of Graft Loss in Renal Transplantation. Clin J Am Soc Nephrol. doi: 10.2215/CJN.07660716 [Epub ahead of print]

2. Foster BJ and Rani Gupta I. Donor Quality in the Eye of the Beholder: Interactions between Nonimmunologic Recipient and Donor Factors as Determinants of Graft Survival. Clin J Am Soc Nephrol 12: ccc–ccc, 2017. doi: 10.2215/CJN.02180217 [Epub ahead of print]

3. Donor-recipient weight and sex mismatch may contribute to kidney transplant failure. [news release] American Society of Nephrology; March 30, 2017.